1. Technical Field
Various embodiments of the present disclosure relate to a nonvolatile memory device and a method of programming the same and, more particularly, to nonvolatile memory devices having a uniform threshold voltage after program and methods of programming the same.
2. Related Art
Electrically erasable programmable read only memory (EEPROM) devices and flash memory devices are nonvolatile memory devices that retain their stored data even during power shut off. Various memory cell structures have been proposed to improve the performance of nonvolatile memory devices. A typical memory cell of a nonvolatile memory device may employ a stack gate structure including a floating gate, an inter-gate dielectric layer and a control gate which are sequentially stacked on a semiconductor substrate. As electronic systems become less with the development of fabrication techniques of semiconductor devices, system-on-chip (SOC) products have been revealed and utilized as important devices of high performance digital systems. SOC products may include a plurality of semiconductor devices executing various functions in a single chip. For example, an SOC product may include a logic device and a memory device integrated in a single chip. Thus, improved fabrication technologies may be required for embedding nonvolatile memory devices in SOC products.
Generally, to embed a nonvolatile memory device in an SOC product, the process technology of the nonvolatile memory device has to be compatible with the process technology of a logic device included in the SOC product. In general, logic devices may employ transistors having a single gate structure, whereas nonvolatile memory devices employ cell transistors having a stack gate structure (i.e., a double gate structure). Thus, SOC products including nonvolatile memory devices and logic devices may require a more complex process technology. Accordingly, single-layered gate nonvolatile memory devices employing a single-layered gate cell structure may be attractive as a candidate of the embedded nonvolatile memory devices. For example, complementary metal-oxide-semiconductor (CMOS) circuits of logic devices may be readily implemented using the process technology of a single-layered gate nonvolatile memory device. As a result, the process technology of single-layered gate nonvolatile memory devices may be widely used in the fabrication of SOC products including embedded nonvolatile memory devices.